Use mysql2:// instead of mysql://

This fixes compatibility with Ruby apps which use the MySQL2 adapter.
Merge pull request #6 from parkr/patch-1

Use mysql2:// instead of mysql://
Fix $IMAGE variable.

(Although this may not matter as it seems as if it's not used in this script.)

In the current version of dokku the $IMAGE variable is no longer passed in to pluginhooks, causing this script to break. The fix is easy, just need to change it from being `IMAGE="$2"` to `IMAGE="app/$APP"`.

More details about the fix, and the commit that changed this, here:
https://github.com/progrium/dokku/issues/313#issuecomment-31210408
Merge pull request #7 from jeresig/patch-1

Fix $IMAGE variable.
Volume path fixes
keep a link to persitent path
Use port instead of IP to persist containers after reboot (still needs a container restart)
path bugfix
meh
Remove post-deploy hook and warn about Docker version
Correct install script since docker broke support of direct github pulling
Correct wrong IP in app linking
Avoid permission fails